Alireza Zarghami

Social Trust-Aware Recommendation System: A T-Index Approach

Collaborative Filtering based on similarity suffers from a variety of problems such as sparsity and scalability. In this paper, we propose an ontological model of trust between users on a social network to address the limitations of similarity measure in Collaborative Filtering algorithms. For enhancing the constructed network of users based on trust, we introduce an estimate of a user’s trustworthiness called T-index to identify and select neighbors in an effective manner. We employ T-index to store raters of an item in a so-called TopTrustee list which provides information about users who might not be accessible within a predefined maximum path length. An empirical evaluation shows that our solution improves both prediction accuracy and coverage of recommendations collected along few edges that connect users on a social network by exploiting T-index. We also analyze effect of T-index on structure of trust network to justify the results.

Decision as a Service: Separating Decision-making from Application Process Logic

In a service-oriented architecture, adaptive and evolvable applications should be able to select, configure and compose different existing application services to deal with the changes which can arise from runtime contextual changes or the change of user requirements and preferences. To support this, hybrid service composition approaches have been proposed, in which the core of application logic, which is rather stable, is specified in terms of processes while rules are employed to specify the conditions and constraints to adapt the application behaviour. The rules are then exposed as a decision service which can be employed by the process to make adaptation decision with respect to runtime circumstances. The interaction between processes and decision services are generally performed in synchronous request-response manner. We argue that such an interaction is not efficient to support different types of adaptation at runtime and therefore asynchronous interaction should also be supported. In this paper, we present an adaptive service provisioning architecture and a decision service template allowing both synchronous request-response interaction and asynchronous notification. To motivate the proposed architecture and the decision service template, we use a blood pressure monitoring scenario from the homecare domain. We also explain the implementation of the proposed approach based on commercially available rule and process engines. Finally, we discuss: 1) what is the efficient way (synchronous request-response interaction vs. asynchronous notification) of calling decision service to execute different types of decision rules? and 2) to what extent the use of decision service facilitates dealing with the unforeseen changes?

Personalized Service Creation by Non-technical Users in the Homecare Domain

One of the conditions for the successful introduction of ICT-based homecare services is to allow non-technical persons such as home nurses to personalize these services. We refer to this process of homecare service personalization as service tailoring. Service tailoring can be done by configuring and composing previously developed and deployed service building blocks. In this paper, we describe an approach that employs predefined information of care-receivers, called user profile, to hide most of the technical details from care-givers who do the service tailoring. First, we define the information to be included in a user profile and patterns that represent composition structures corresponding to common homecare tasks experienced in homecare. Then, we define how the service tailoring process can exploit information contained in the predefined user profiles. After that, we illustrate the approach with a tailoring scenario.

Achieving Flexible Process Interoperability in the Homecare Domain through Aspect-Oriented Service Composition

In elderly care the shortage of available financial and human resources for coping with an increasing number of elderly people becomes critical. Current solutions to this problem focus on efficiency gains through the usage of information systems and include homecare services provided by IT systems. However, the current IT systems that integrate homecare services have difficulties in handling the user-context dynamicity and the diversity of needs and preferences of care-receivers. This makes the available homecare services hardly interoperable at the process level, particularly due to the lack of support for process flexibility. In this paper, we present an approach capable of dealing with such interoperability issues based on aspect-oriented service composition. We demonstrate the feasibility of our approach and of the proposed architecture by implementing a prototype for a reminder service scenario.

Dynamic homecare service provisioning architecture

The realization of homecare services is difficult because of dynamicity requirements and constraints that exist in this domain. These requirements call for a dynamic service provisioning, i.e., adaptivity and adaptability of the (composition of) homecare services in response to a) frequently occurring changes like change in the location or vital signs, or b) slowly developing changes like extent of impairments of a care-receiver. In this paper, we explain our understanding of a dynamic service provisioning platform, its requirements and constraints. As such, we design an architecture based on an existing hybrid service provisioning approach (a combination of process and rule) and related architectural patterns. Then, we implement this approach using the commercially available process and rule engines. We demonstrate how a homecare application can be deployed, executed and how the application can adapt itself to the frequently occurring changes at runtime. We also demonstrated how a care-giver can modify the behaviour of the application to adapt the slowly occurring changes. Finally, we discuss the pros and cons of the approach and explain our future plan.

Mechanizing social trust-aware recommenders with T-index augmented trustworthiness

Social Networks have dominated growth and popularity of the Web to an extent which has never been witnessed before. Such popularity puts forward issue of trust to the participants of Social Networks. Collaborative Filtering Recommenders have been among many systems which have begun taking full advantage of Social Trust phenomena for generating more accurate predictions. For analyzing the evolution of constructed networks of trust, we utilize Collaborative Filtering enhanced with T-index as an estimate of a users trustworthiness to identify and select neighbors in an effective manner. Our empirical evaluation demonstrates how T-index improves the Trust Network structure by generating connections to more trustworthy users. We also show that exploiting T-index results in better prediction accuracy and coverage of recommendations collected along few edges that connect users on a network.

Dynamic Homecare Service Provisioning: A Field Test and Its Results

Providing IT-based care support for elderly at home is proposed as a highly promising appraoch to address the aging population problem. With the emergence of homecare application service providers, a homecare system can be seen as a linked set of services. Configuring and composing existing homecare application services to create new homecare composite applications can reduce the application development cost. The idea even looks more promising if the service provisioning is dynamic, i.e., if applications can update their behaviors with respect to the contextual changes without or with minimum manpower. Dynamic service provisioning can play an important role to accept homecare systems in practical settings. This motivated us to develop a Dynamic Homecare Service Provisioning (DHSP) platform to address the homecare context changes in an effective and efficient manner. As a proof of concept, we have developed a software prototype of our platform. The prototype was subsequently used in a real-world field test at a care institution in the Netherlands to validate the approach. This paper describes the design of the field test and reflects on the outcome of the validation experiments.

Assumption-based risk identification method (ARM) in dynamic service provisioning

In this paper we consider service-oriented applications composed of component services provided by different, economically independent service providers. As in all composite applications, the component services are composed and configured to meet requirements for the composite application. However, in a field experiment of composite service-oriented applications wef found that, although the services as actually delivered by the service providers meet their requirements, there is still a mismatch across service providers due to unstated assumptions, and that this mismatch causes an incorrect composite application to be delivered to end-users. Identifying and analyzing these initially unstated assumptions turns requirements engineering for service-oriented applications into risk analysis. In this paper, we describe a field experiment with an experimental service-oriented homecare system, in which unexpected behavior of the system turned up unstated assumptions about the contributing service providers. We then present an assumptions-driven risk identification method that can help identifying these risks, and we show how we applied this method in the second iteration of the field experiment. The method adapts some techniques from problem frame diagrams to identify relevant assumptions on service providers. The method is informal, and takes the “view from nowhere” in that it does not result in a specification of the component services, but for every component service delivers a set of assumptions that the service must satisfy in order to contribute to the overall system requirements. We end the paper with a discussion of generalizability of this method.